Antistatic photographic film



A. S. MCDANIEL.

ANTISTATIC PHOTOGRAPHIC FILM.

APPLICATION FILED MAR. 26, 192|.

Patnted Oct. 10, 1922.

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WITNESS @mM/W m' .0 AUI@ '3,

1Z0 INVENgZe ATTORNEYS.

Patented Oct. l0, 1922.

UNITED STATES ALONZO S. MGDANIEL, OF NEW YORK, N. Y.,

ASSIGNOR T0 EASTMAN KODAK COMPANY,

OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

ANTISTATIC PHOTOGRAPHIC FILM.

Application led March 26, 1921.

To all whom t may concern:

Be it known that I, ALONZO S. MGDANIEL, a citizen of the United States of America, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Antistatic Photographic Films, of which the following is a full, clear, and exact specification. v

This invention relates to photographic film. The principalobject of this invention is to provide a film having the qualities desirable in commercial practice, which will likewise be so made that markings due to electric discharges are prevented or very greatly minimized.

ln the handling of sensitive photographic film, particularly that of the usual kind, which includes a nitrocellulose support or base, characteristic lines or patches sometimes appear on development due to elec-- tric discharges which occur when the film is manipulated. lVhile the defect may crop out during manufacture, it ispartic-ularly troublesome in the motion picture ield,espe cially when making negative iilm strips. 1t is customarily referred to as static and will be so designated hereafter.

There have been suggested at different times various methods of combating this evil, among which may be mentioned the application to the back of a film of a soluble gum-like substance, as in British `atent No. 13,088, Mellersh-Jackson, filed June 15, 1913, or the incorporation in the nitrocellulose base of various salts, some of which have hygroscopic properties, this being described in U. S. Patent No. 584,862, Eastman, June 22, 1897, BritishPatent No. 7501, Boult, filed Apr. 20, 1892, and German Patent No.,69,231, Eastman Photographic Materials Coti" Ltd.,

YMay 16, 1893. These also describe the use of a metallic salt 4in a gelatine layer on the back of the ilm. It may be noted thatthe gelatine layer would necessarily be more or less softened while wet from the photographic baths. While a gelatine backing is useful in preventing static, one objection to its use on motion picture film is that much of the apparatus ordinarily used in treating film comprises racks, bars and drums which the lihn passes, or against whch it lies during treatment and if the film has a soft backing this becomes objectionably scratched Serial No. 455,816.

be either entirely removed or substantially..

unaffected by the photographiebaths. In the patent to Lovejoy No. 1,232,702, July 10, 1917, there is described a support fory a photographic lilm in which cellulose acetate and cellulose nitrate are both used, and as there fully set forth, these two substances tend to neutralize each others tendencies toward the generation of static electricity during the passage of the iilm over friction surfaces. A support made in accordance with this patent is not affected by the photographic baths.

lWhile l have found that .film made in the manner described in this patent to be efficient, l have discovered that it is made even more efficient by the introduction of a deliquescent metallic salt into the film base or support". l l

ln order to explain more fully the structure of the film, reference will now be made to the drawings in which:

Fig. 1 is a cross section on a large scale of a photographic film made in accordance with the preferred form of my invention;

Figs. 2, 3 and 4 are similar sections of alternative forms of my invention.

1n the drawings, the sensitive layer is indicated as 1. This is carried by a support which comprises both cellulose nitrate and cellulose acetate. These may, if desired, be in two separate layers, the nitrate and acetate being indicated at 2 and 3 respectively in Fig. 1, or they may be incorporated in a common layer as shown at 4 in Fig. 2. The various ways in which this film may be made are fully described in the patent to Lovejoy mentioned. Thus the layer 41 may, as shown in F ig. 3, be a mixture of acetate and nitrate containing the hygroscopic material 1 and 2 representing in this figure respectively the photographically sensitive layer and the nitrocellulose layer, and the nitros' cellulose being between the other two. Als the layer 31 in Fig. 4 may be the layer o cellulose acetate containing the hygroscop-iy ic material, the photographicall7 sensitive layer being on one side of it, while the nitrocellulose layer 2 is on the other side of it. Of course, the relative thicknesses ofiE the various layers canyary great1y,'the di-' l layers,

mensions in the drawing being exaggerated for the sake of clearness. p

In the preferred form of my invention, l incorporate into the material of one ofthe acetate, acertain amount of hygroscopic material, preferably a deliquescent metallic salt. The particular formula of the do e is not essential; many such compositions are known and l contemplate the use ot such of these asl are referred to in the Lovejoy patent. A salt which l find highly satisfactory is calcimum chloride. The quantity of salt introduced into the material of the support may vary within wide limits. A distinctly beneficial efiect is observed when to a mass of the dope there is added as little as .05% of calciun'rchloride. The effect is noticeably better, 'particularly when from 1% to 2% is used, and l have used as much as 3% with good results. l wouldconsider 3% as about the upper desirable limit of the amount to be used. lt is to be noted that in every case the deliquescent salt is incorporated in the material of the support itself, that is to say, in a layer which is a permanent part of the support of the film, and which is for all substantial purposes unaffected and unsoftened by and insoluble in the ordinary photographic baths. This is true even though the layer containing the deliquescent salt is a thin backing layer, and in my preferred form this is the case, the backing layer being the layer containing cellulose acetate. It may be noted that this is to be distinguished from a support containing nitrate only, and also from a support containing a l: er such as gelatine or dextrine which will either be softened by or soluble in the developing baths, or from any other layer, whether containing Isalts or'not, de'

posited lon the back surface of. the film, which is removed entirely during photographic manipulations.

Having thus described my invention, what I claim as) new anddesire to secure by Letters Patent is:

1. A photographic film comprising a film support, a layer of sensitive material carried thereby and a layer of material which is unsoftened by photographic baths and containing a hygroscopic material.

2. An anti-static photographic film comprising a film support, a layer of sensitive material carried thereby and a backing layer of material insoluble in andunsoften-ed by photographic baths and containing'a deliquescent material.

3. An anti-static photographic film comprising a layer of photographic sensitive material and a support therefor, the support comprising cellulose nitrate and cellulose fdeliquescent metallic aphic film comprnsmg a layer 6 and preferably that layer containing trate, and a acetate and' having inclorporated therein a sa t.

, 4. A photogr o-sensitive material and a support theretor, the support comprising in separate layers two substances respectively adapted to de-4 4 velop positive and negative static charges when acted upon frictionally, one of said layers having incorporated therein hygroscopic material. V

5. A hotographic film comprising a la er of sensitive material and a support there or, the support comprising in .separate layers two substances respectlvely adapted to develop positive and negative static charges when acted upon frictionally, one of said layers having incorporated therein a deliquescent metallic salt.

6. A photographic iilm comprising a layer of sensitive material and a support theretor, the support comprising in separate layers two substances respectively adapted to develop positive and negative static charges when acted upon frictionally, one of said layers having calcium chloride incorporated therein.

7. A photographic film comprising a layer of sensitive material and a support comprising a layer of cellulose nitrate and a layer .YAn anti-static photographic film lcomprlsmg a la er of photographically sensitive materia, a layer comprising cellulose' nitrate and a backing layer containing cellulose acetate, the backing layer containing a deliquescent metallic salt.

9. An anti-static photographic film comprising a layer of photographically sensitive material, a layer comprising cellulose nitrate and a backing layer containing cellulose acetate, the backing layer having calcium'chloride incorporated therein. p

10. An anti-static photographic film comprising a layervof photographically sensitive material, a layer comprising cellulose nitrate, and a backing layer, said backing layer containing cellulose acetate, and having incorporated therein not to exceed 3 per cent of a deliquescent metallic salt.

11. An anti-static photographic film comprising a layer of photographically sensitive material, a la er comprising cellulose niacking. layer, said backing layer containing cellulose acetate, and havincorporated therein not to exceed 3 per cent of calcium chloride.

Signed at New York, New York, this 22nd day of March 1921. 

